It is known to monitor dry pump condition by observing surges in motor torque or current. This is not, however, an ideal method of predicting pump failure. A pump will usually operate without any noticeable problem while deposits gradually build-up in the running clearances. This build-up usually takes place over a long period of time and eventually there will be contact, or rubbing, between two parts. When this happens, the heat generated causes thermal expansion, thus increasing the rubbing and causing further thermal expansion, often leading to seizure and pump failure. This contact, or rubbing, can be detected as a surge in motor current. However, the time between detection of a current surge and pump failure can be short, and in the case of a dry pump there is usually insufficient time to take action following the detection of a current surge.
Pump failure due to seizure is always undesirable, but is even more of a problem where the pump is being used in a manufacturing process and the pump failure leads to the loss of a batch of product. For example, if a vacuum pump fails during the production of semi conductors, typically the batch of parts affected has to be rejected, which can be very expensive. In order to avoid the problem, pumps can be stripped down and parts replaced or cleaned as part of a planned period maintenance system. However, this can result in unnecessary expense as to be safe, the pumps have to be serviced more frequently than is actually necessary.
In addition to problems associated with deposits forming in pumps, the efficiency of a pump and the system in which it operates can be adversely affected by the build-up of process by-products in the pump exhaust, piping connected to the exhaust and/or the pump itself.
Yet another problem with pumps that can lead to pump failure is undetected bearing wear.